Tejede Circuit ọkọ (PCB) ni a rii ni o fẹrẹ to gbogbo iru ẹrọ itanna. If there are electronic components in a piece of equipment, they are also embedded in various sizes of PCB. In addition to fixing various small parts, the main function of the PCB is to provide electrical connections between the components. As electronic equipment becomes more and more complex, more and more parts are needed, and the wiring and parts on the PCB become more and more dense. PCB boṣewa kan dabi nkan bi eyi. Bare Board (without parts on it) is also often referred to as “Printed Wiring Board (PWB).

The substrate of the board itself is made of a material that is insulated and resistant to bending. The small line material that can be seen on the surface is copper foil. Originally, the copper foil is covered on the whole board, and the middle part is etched away in the manufacturing process, and the remaining part becomes a network of small lines. These lines are called conductors or conductors and are used to provide electrical connections to parts on the PCB.

To secure parts to the PCB, we solder their pins directly to the wiring. Lori PCB ipilẹ, awọn apakan wa ni ogidi ni ẹgbẹ kan ati awọn okun waya wa ni ogidi lori ekeji. So we need to make holes in the board so that the pins can go through the board to the other side, so the pins of the parts are welded to the other side. Because of this, the front and back sides of a PCB are called Component Side and Solder Side respectively.

Ti awọn ẹya ba wa lori PCB ti o le yọ kuro tabi tun pada lẹhin iṣelọpọ, Socket yoo lo lati fi awọn ẹya sii. Because the socket is directly welded to the board, the parts can be arbitrarily disassembled. A ZIF (Zero InserTIon Force) plug allows parts to be inserted and removed easily. The lever next to the socket can hold the parts in place after you insert them.

To connect two PCBS to each other, an edge connector is commonly used. Ika goolu ni nọmba kan ti awọn paadi idẹ ti ko ni igboro ti o jẹ apakan gangan ti wiwa PCB. Ni deede, lati sopọ, a fi ika goolu sii lori PCB kan sinu Iho ti o yẹ (eyiti a pe ni iho imugboroosi) lori PCB miiran. In computers, display cards, sound cards, and similar interface cards are connected to the motherboard by means of a gold finger.

Awọ alawọ ewe tabi awọ brown lori PCB jẹ awọ ti iboju ti o ta. This layer is an insulating shield that protects the copper wire and prevents parts from being welded to the wrong place. Miran ti siliki iboju yoo wa ni tejede lori solder resistance Layer. It is usually printed with words and symbols (mostly white) to indicate the position of the parts on the board. Screen printing surface is also known as icon surface

Àlàyé).

Nikan-apa Boards

Gẹgẹbi a ti mẹnuba, lori PCB ipilẹ, awọn apakan wa ni ogidi ni ẹgbẹ kan ati awọn okun waya wa ni ogidi lori ekeji. Because the wire appears on only one side, we call this TYPE of PCB single-sided. Nitori awọn panẹli ẹyọkan ni ọpọlọpọ awọn ihamọ ti o muna lori apẹrẹ ti Circuit (nitori pe ẹgbẹ kan ṣoṣo ni o wa, wiwa ko le rekọja ati pe o ni lati gba ọna lọtọ), awọn iyika kutukutu nikan lo iru awọn igbimọ bẹ.

Meji-lọọgan Boards

Igbimọ Circuit ni wiwu ni ẹgbẹ mejeeji. But in order to use both wires, there must be proper electrical connections between the two sides. “Afara” yii laarin awọn iyika ni a pe ni iho itọsọna (VIA). Awọn iho itọsọna jẹ awọn iho kekere ninu PCB ti o kun tabi ti a bo pẹlu irin ti o le sopọ si awọn okun onirin ni ẹgbẹ mejeeji. Because a dual panel has twice the area of a single panel, and because the wiring can be interlaced (it can be wound around to the other side), it is better for more complex circuits than a single panel.

Multi-layer Boards

Lati le pọ si agbegbe ti o le firanṣẹ, diẹ sii ni ẹyọkan-tabi awọn igbimọ wiwisi ni ilopo-meji ni a lo. Igbimọ multilayer nlo ọpọlọpọ awọn paneli ilọpo meji, ati pe a ti fi fẹlẹfẹlẹ kan ti idabobo laarin paneli kọọkan ati lẹ pọ (tẹ). The number of layers of the board represents several independent wiring layers, usually an even number of layers, including the outermost two layers. Most motherboards are built with four to eight layers, but it is technically possible to build up to 100 layers of PCBS. Pupọ awọn kọnputa nla nla lo awọn fẹlẹfẹlẹ diẹ ti awọn modaboudu, ṣugbọn wọn ti ṣubu ni lilo bi wọn ṣe le rọpo nipasẹ awọn iṣupọ ti awọn kọnputa lasan. Because the layers in a PCB are so tightly integrated, it’s not always easy to see the actual number, but if you look closely at the motherboard, you might be able to.

The guide hole (VIA) we just mentioned, if applied to a double panel, must be through the entire board

But in a multilayer, if you only want to connect some of the lines, the guide holes may waste some of the line space in the other layers. Buried vias and Blind vias avoid this problem because they only penetrate a few layers. Blind holes connect several layers of internal PCBS to surface PCBS without penetrating the entire board. Buried holes are only connected to the internal PCB, so light is not visible from the surface.

In a multilayer PCB, the entire layer is directly connected to the ground wire and the power supply. So we classify the layers as Signal, Power or Ground. If the parts on the PCB require different power supplies, they usually have more than two power and wire layers.

Imọ -ẹrọ iṣakojọpọ apakan

Nipasẹ Iho Technology

The technique of placing parts on one side of the board and welding the pins to the other side is called “Through Hole Technology (THT)” encapsulation. This part takes up a lot of space and one hole is drilled for each pin. Nitorinaa awọn isẹpo wọn gangan gba aaye ni ẹgbẹ mejeeji, ati awọn isẹpo solder jẹ iwọn nla. Ni apa keji, awọn ẹya THT ni asopọ daradara si PCB ju awọn apakan Imọ -ẹrọ Imọlẹ Oorun (SMT), eyiti a yoo sọrọ nipa nigbamii. Sockets like wired sockets and similar interfaces need to be pressure-tolerant, so they are usually THT packages.

Surface Mounted Technology

For Surface Mounted Technology (SMT) parts, the pin is welded on the same side with the parts. This technique does not drill holes in the PCB for each pin.

Awọn ẹya alemora dada le paapaa jẹ alurinmorin ni ẹgbẹ mejeeji.

SMT tun ni awọn ẹya kekere ju THT lọ. Compared to PCB with THT parts, PCB with SMT technology is much denser. SMT package parts are also less expensive than THT’s. So it’s no surprise that most of today’s PCBS are SMT.

Because the solder joints and pins of parts are very small, it is very difficult to weld them manually. However, given that current assembly is fully automated, this problem will only occur when repairing parts.

The design process

Ni apẹrẹ PCB, awọn igbesẹ gigun gaan wa gaan lati lọ ṣaaju wiwa wiwọ. Awọn atẹle jẹ ilana apẹrẹ akọkọ:

The system specifications

First of all, the system specifications of the electronic equipment should be planned. It covers system functionality, cost constraints, size, operation and so on.

System function block diagram

Igbesẹ ti n tẹle ni lati ṣẹda aworan apẹrẹ iṣẹ ṣiṣe ti eto naa. Ibasepo laarin awọn onigun mẹrin gbọdọ tun samisi.

Divide the system into several PCBS

Dividing the system into several PCBS not only reduces the size, but also gives the system the ability to upgrade and swap parts. The system function block diagram provides the basis for our segmentation. Computers, for example, can be divided into motherboards, display cards, sound cards, floppy disk drives, power supplies, and so on.

Pinnu ọna apoti lati ṣee lo ati iwọn PCB kọọkan

Once the technology and the number of circuits used for each PCB has been determined, the next step is to determine the size of the board. If the design is too large, then packaging technology will have to change, or re-split the action. Didara ati iyara ti aworan Circuit yẹ ki o tun ṣe akiyesi nigbati yiyan imọ -ẹrọ.

Draw schematic circuit diagrams of all PCB’s

The details of the interconnections between the parts should be shown in the sketch. PCB ni gbogbo awọn eto gbọdọ wa ni apejuwe, ati pupọ julọ wọn lo CAD (Apẹrẹ Iranlọwọ Kọmputa) ni lọwọlọwọ. Here is an example of a CircuitMakerTM design.

Aworan atọka ti Circuit PCB

Preliminary design of simulation operation

To ensure that the designed circuit diagram works, it must first be simulated using computer software. Such software can read blueprints and show how the circuit works in many ways. This is much more efficient than actually making a sample PCB and then measuring it manually.

Place the parts on the PCB

The way parts are placed depends on how they are connected to each other. Wọn gbọdọ wa ni asopọ si ọna ni ọna ti o munadoko julọ. Efficient wiring means the shortest possible wiring and fewer layers (which also reduces the number of guide holes), but we’ll come back to this in actual wiring. Here is what the bus looks like on a PCB. Placement is important in order for each part to have perfect wiring.

Test wiring possibilities with correct operation at high speed

Diẹ ninu sọfitiwia kọnputa oni le ṣayẹwo boya gbigbe ti paati kọọkan le sopọ ni deede, tabi ṣayẹwo boya o le ṣiṣẹ ni deede ni iyara to gaju. Igbesẹ yii ni a pe ni siseto awọn apakan, ṣugbọn a kii yoo lọ jinna si eyi. Ti iṣoro ba wa pẹlu apẹrẹ Circuit, awọn ẹya tun le ṣe atunto ṣaaju ki Circuit ti okeere ni aaye.

Okeere Circuit lori PCB

The connections in the sketch will now look like wiring in the field. Igbesẹ yii jẹ adaṣe adaṣe ni kikun, botilẹjẹpe awọn ayipada afọwọṣe nigbagbogbo nilo. Below is the wire template for 2 laminates. Awọn laini pupa ati buluu ṣe aṣoju Layer awọn ẹya PCB ati fẹlẹfẹlẹ alurinmorin lẹsẹsẹ. The white text and squares represent the markings on the screen printing surface. Awọn aami pupa ati awọn iyika ṣe aṣoju liluho ati awọn ihò didari. Ni apa ọtun ọtun a le rii ika goolu lori ilẹ alurinmorin ti PCB. The final composition of this PCB is often referred to as the working Artwork.

Each design must conform to a set of rules, such as minimum reserved gaps between lines, minimum line widths, and other similar practical limitations. Awọn pato wọnyi yatọ gẹgẹ bi iyara ti Circuit, agbara ti ifihan lati gbejade, ifamọ ti Circuit si agbara agbara ati ariwo, ati didara ohun elo ati ẹrọ iṣelọpọ. If the strength of the current increases, the thickness of the wire must also increase. In order to reduce PCB costs, while reducing the number of layers, it is also necessary to pay attention to whether these regulations are still met. Ti o ba nilo diẹ sii ju awọn fẹlẹfẹlẹ 2 lọ, fẹlẹfẹlẹ agbara ati fẹlẹfẹlẹ ilẹ ni igbagbogbo lo lati yago fun ifihan gbigbe lori fẹlẹfẹlẹ ifihan yoo kan, ati pe o le ṣee lo bi asà ti fẹlẹfẹlẹ ifihan.

Wire after circuit test

In order to be sure that the line is working properly behind the wire, it must pass the final test. Idanwo yii tun ṣayẹwo fun awọn asopọ ti ko tọ, ati gbogbo awọn isopọ tẹle aworan apẹrẹ.

Fi idi mulẹ ati faili

Nitori ọpọlọpọ awọn irinṣẹ CAD lọwọlọwọ fun apẹrẹ PCBS, awọn aṣelọpọ gbọdọ ni profaili kan ti o pade awọn ajohunše ṣaaju ki wọn to le ṣe awọn igbimọ. There are several standard specifications, but the most common is the Gerber Files specification. A set of Gerber files includes a plan of each signal, power and ground layer, a plan of the solder resistance layer and the screen printing surface, and specified files of drilling and displacing.

Electromagnetic compatibility problem

Awọn ẹrọ itanna ti ko ṣe apẹrẹ si awọn pato EMC ni o ṣee ṣe lati mu agbara itanna ṣiṣẹ ati dabaru pẹlu awọn ohun elo nitosi. EMC ṣe awọn idiwọn ti o pọju lori kikọlu itanna (EMI), aaye itanna (EMF) ati kikọlu igbohunsafẹfẹ redio (RFI). Ilana yii le rii daju iṣiṣẹ deede ti ohun elo ati awọn ohun elo miiran nitosi. EMC ṣe awọn idiwọn to muna lori iye agbara ti o le tuka tabi tan kaakiri lati ẹrọ kan si omiiran, ati pe a ṣe apẹrẹ lati dinku ifura si EMF ita, EMI, RFI, ati bẹbẹ lọ. In other words, the purpose of this regulation is to prevent electromagnetic energy from entering or emanating from the device. This is a very difficult problem to solve, and is usually solved by using power and grounding layers, or putting PCBS into metal boxes. The power and ground layers protect the signal layer from interference, and the metal box works equally well. We won’t go too far into these issues.

The maximum speed of the circuit depends on EMC compliance. EMI inu, gẹgẹbi pipadanu lọwọlọwọ laarin awọn oludari, pọ si bi igbohunsafẹfẹ ba ga soke. Ti iyatọ lọwọlọwọ laarin awọn mejeeji tobi pupọ, rii daju lati fa gigun aaye laarin wọn. This also tells us how to avoid high voltage and minimize the current consumption of the circuit. Oṣuwọn idaduro ni wiwa tun jẹ pataki, nitorinaa kikuru gigun, dara julọ. Nitorinaa PCB kekere kan pẹlu okun waya to dara yoo ṣiṣẹ dara ni awọn iyara giga ju PCB nla kan.